Apparatus for opening/closing chin protection bar of safety helmet and safety helmet having the same

ABSTRACT

There is provided an apparatus for opening/closing a chin protection bar installed in a helmet cap having a front opening, the apparatus including: a fixing unit which is fixed to the helmet cap and includes a movable shaft guide having an elongated hole shape and a pivoting guide formed approximately vertical to the movable shaft guide; and a pivoting unit which is fixed to the chin protection bar and includes a first connecting unit slidably inserted into the movable shaft guide and a second connecting unit slidably inserted into the pivoting guide, wherein the pivoting guide has a straight line shape, and the second connecting unit moves back and forth in a straight line in the pivoting guide and the first connecting unit moves back and forth in a straight line in the movable shaft guide according to the straight-line back-and-forth movement of the second connecting unit.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No. 10-2007-0105042, filed on Oct. 18, 2007, the entire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to a chin protection bar opening/closing apparatus for a safety helmet. More particularly, the present invention relates to the chin protection bar opening/closing apparatus which is simple in structure but capable of preventing the chin protection bar from colliding with other attachments of the safety helmet while opening or closing the chin protection bar.

BACKGROUND OF THE INVENTION

Motorcycle safety helmets generally have a front opening to allow a wearer to obtain a front view and a shield to prevent sight obstruction and breathing difficulty due to winds blowing from the front of the wearer while the motorcycle moves forward.

In general, among such motorcycle safety helmets, there are a full-face type helmet in which a chin protection bar for protect a chin is integrally provided for a safety helmet and an opening/closing type helmet in which a chin protection bar can be opened and closed.

The chin protection bar in the opening/closing-type helmet capable of opening/closing the chin protection bar can be moved up to an upper portion of the helmet when it is rotated backward, and when the chin protection bar is rotated forward, it is locked by a locking device so as to protect the chin.

A rotation movement of the chin protection bar is made from a hinge shaft installed in two right and left sides of the helmet. Therefore, if the chin protection bar can make only a simple rotation movement, there has been a problem that an opening/closing chin protection bar is collided with other attachment such as a front side of the helmet and a part of an air vent passage.

In order to solve such a problem, the chin protection bar should be rotated at a predetermined distance away from the helmet while the chin protection bar is opened and closed, and a conventional chin protection bar opening/closing apparatus employing this structure is illustrated in FIG. 1.

FIG. 1 is an exploded perspective view of the conventional chin protection bar opening/closing apparatus.

As shown in FIG. 1, the conventional chin protection bar opening/closing apparatus 40 includes a fixing plate 41 fixed at a helmet body, an operation plate 42 fixed at the chin protection bar, a planetary gear 43, a pivoting lever 44 and the like. If the wearer rotates the chin protection bar backward, the chin protection bar is rotated while an upward guide protuberance 42 a of the operation plate 42 is inserted into an arc-shaped guide hole 41 a of the fixing plate 41. A protruding part 41 b is formed in a part of the middle portion of the arc-shaped guide hole 41 a in a reverse direction of the arc shape so that when the upward guide protuberance 42 a reaches the upper portion of the protruding part 41 b (i.e., when the upward guide protuberance 42 a is positioned in the lowest position of the arc-shaped guide hole 41 a), the operation plate 42 becomes spaced from the fixing plate 41 by a predetermined distance and the chin protection bar eventually is spaced from the helmet body by a predetermined distance accordingly.

However, even though the conventional chin protection bar opening/closing apparatus 40 has an advantage that the chin protection bar is rotated at a predetermined distance away from the helmet body, the chin protection bar opening/closing apparatus 40 includes various kinds of parts installed therein and also a connection structure among its parts is very complicated. Therefore, there has been a problem that a manufacturing cost of the helmet becomes higher and the total weight of the helmet becomes increased.

BRIEF SUMMARY OF THE INVENTION

In view of the foregoing, an embodiment of the present invention is provided to solve the problem and the present invention has an object to provide a chin protection bar opening/closing apparatus which is simple in structure and capable of allowing the chin protection bar to rotate while being spaced apart from the helmet cap by a predetermined distance.

To achieve the above-mentioned object, in accordance with a first aspect of the present invention, there is provided an apparatus for opening/closing a chin protection bar installed in a helmet cap having a front opening, the apparatus including: a fixing unit which is fixed to the helmet cap and includes a movable shaft guide having an elongated hole shape and a pivoting guide formed approximately vertical to the movable shaft guide; and a pivoting unit which is fixed to the chin protection bar and includes a first connecting unit slidably inserted into the movable shaft guide and a second connecting unit slidably inserted into the pivoting guide, wherein the pivoting guide has a straight line shape, and the second connecting unit moves back and forth in a straight line in the pivoting guide and the first connecting unit moves back and forth in a straight line in the movable shaft guide according to the straight-line back-and-forth movement of the second connecting unit.

Further, if the second connecting unit moves from one end of the pivoting guide to the middle portion thereof, the first connecting unit can be lifted from a lower side of the movable shaft guide to a upper side thereof and if the second connecting unit moves from the middle portion of the pivoting guide to the other end thereof, the first connecting unit can be lowered from the upper side of the movable shaft guide to the lower side thereof.

Furthermore, the first connecting unit of the pivoting unit may include a first plate and a first shaft part connected to a part of a lower side of the first plate, and the second connecting unit may include a second plate and a second shaft part connected to a part of a lower side of the second plate.

Further, the movable shaft guide of the fixing unit may include a first hole into which the first plate can be inserted and a second hole, which has approximately the same width as that of the first shaft and can be elongated in order for the first connecting unit passing through the first hole to move in a straight line.

Furthermore, the pivoting guide of the fixing unit has a stepped protrusion, whereby the second plate passing through the pivoting guide can slide while being hooked on the stepped portion so as to prevent the second connecting unit from being separated from the pivoting guide.

Further, if the first connecting unit is disposed in one end of the second hole in a direction opposite to the first hole, the second connecting unit can be elastically supported against the stepped portion.

Furthermore, a stopper protrusion for limiting a rotation of the chin protection bar can be formed in one side of the pivoting unit and a stopper hook corresponding to the stopper protrusion can be formed in one side of the fixing unit.

In accordance with a first aspect of the present invention, there is provided a safety helmet, including: a helmet cap having a front opening; a chin protection bar which is pivotably fixed at the helmet cap for protecting a wearer's chin; and a chin protection bar opening/closing apparatus which serves as a pivoting shaft of the chin protection bar and at the same time allows the chin protection bar to rotate while being spaced apart from the helmet cap by a predetermined distance, wherein the chin protection bar opening/closing apparatus includes: a fixing unit which is fixed at the helmet cap and has a long hole-shaped movable shaft guide and a pivoting guide formed approximately vertical to the movable shaft guide; and a pivoting unit which is fixed at the chin protection bar and has a first connecting unit slidably inserted and connected to the movable shaft guide and a second connecting unit slidably inserted into the pivoting guide, wherein the pivoting guide has a straight line shape and the second connecting unit moves back and forth in a straight line in the pivoting guide and the first connecting unit moves back and forth in a straight line in the movable shaft guide according to the straight-line back-and-forth movement of the second connecting unit.

In accordance with an embodiment of the present invention, it is possible to provide the chin protection bar opening/closing apparatus which is simple in structure but capable of preventing the chin protection bar from colliding with the helmet body because the chin protection bar is rotated at a predetermined distance away from the helmet body.

Further, in accordance with an embodiment of the present invention, it is possible to reduce the total weight of the helmet as well as the manufacturing cost of the helmet by employing a simple structure of the chin protection bar opening/closing apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may best be understood by reference to the following description taken in conjunction with the following figures:

FIG. 1 is an exploded perspective view of a conventional chin protection bar opening/closing apparatus;

FIG. 2 is a whole perspective view of a chin protection bar and a safety helmet employing the chin protection bar in accordance with an embodiment of the present invention;

FIG. 3 shows an exploded perspective view of a chin protection bar opening/closing apparatus in accordance with the embodiment of the present invention;

FIG. 4 is a side view of a pivoting unit of the chin protection bar opening/closing apparatus in accordance with the embodiment of the present invention;

FIG. 5 illustrates a detailed view of a connection between the pivoting unit and a fixing unit of the chin protection bar opening/closing apparatus in accordance with an embodiment of the present invention;

FIG. 6 is a partial side view illustrating a state of the chin protection bar opening/closing apparatus prior to operation thereof in accordance with an embodiment of the present invention;

FIG. 7 is a partial side view of a state of the chin protection bar opening/closing apparatus under operation thereof in accordance with an embodiment of the present invention; and

FIG. 8 is a partial side view of a sate of the chin protection bar opening/closing apparatus after operation thereof in accordance with an embodiment of the present invention.

EXPLANATION OF CODES

-   40: Chin protection bar opening/closing apparatus -   41: Fixing plate -   42: Operation plate -   43: Planetary gear -   44: Pivoting lever -   100: Helmet cap -   200: Locker -   300: Chin protection bar opening/closing apparatus -   400: Fixing unit -   410: Movable shaft guide -   430: Pivoting guide -   432: Stepped protrusion -   440: Stopper protrusion -   500: Pivoting unit -   510: First connecting unit -   511: First plate -   512: First shaft part -   520: Second connecting unit -   521: Second plate -   522: Second shaft part -   530: Stopper hook -   600: Front opening -   700: Chin protection bar

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that the present invention may be readily implemented by those skilled in the art. However, it is to be noted that the present invention is not limited to the embodiments but can be realized in various other ways. In the drawings, parts irrelevant to the description are omitted for the simplicity of explanation, and like reference numerals denote like parts through the whole document.

Through the whole document, the term “connected to” or “coupled to” that is used to designate a connection or coupling of one element to another element includes both a case that an element is “directly connected or coupled to” another element and a case that an element is “electronically connected or coupled to” another element via still another element. Further, the term “comprises or includes” and/or “comprising or including” used in the document means that one or more other components, steps, operation and/or existence or addition of elements are not excluded in addition to the described components, steps, operation and/or elements.

FIG. 2 is a perspective view of a safety helmet in accordance with an embodiment of the present invention.

As shown in FIG. 2, the safety helmet in accordance with the present invention includes a helmet cap 100 containing a front opening 600; a chin protection bar 700 for protecting a wearer's chin during the ride; a locker 200 for fixing the chin protection bar 700 at the helmet cap 100 when the chin protection bar 700 is totally rotated to the front of the helmet cap 100; and a chin protection bar opening/closing apparatus 300 for allowing the chin protection bar to rotate while being spaced apart from the helmet cap by a predetermined distance.

The helmet cap 100 is the most external part of the safety helmet and serves as a structural frame for maintaining a shape of the helmet. The safety helmet should have a sufficient rigidity to maintain an original shape of the helmet without being transformed against any external forces but if it has too strong a rigidity, the helmet can be broken on a collision course so that it is needed to use a material having ductility as well.

When the chin protection bar 700 is rotated backward, it is moved up to an upper portion of the helmet and when the chin protection bar 700 is rotated forward, it is fixed at the helmet cap 100 by a locker so as to protect the chin.

The chin protection bar opening/closing apparatus 300 serves as a pivoting shaft for the helmet cap 100 of the chin protection bar 700 and spaces the chin protection bar 700 apart from the helmet cap 100 by a predetermined distance.

FIG. 3 is an exploded perspective view of the chin protection bar opening/closing apparatus 300 in accordance with the embodiment of the present invention.

As illustrated in FIG. 3, the chin protection bar opening/closing apparatus 300 includes a fixing unit 400 fixed at left and right sides of the helmet cap 100 and a pivoting unit 500 fixed at an inner side of right and left extending portions 710 (illustrated in FIG. 5) of the chin protection bar 700.

The fixing unit 400 includes a elongated movable shaft guide 410; a pivoting guide 430 formed in an opposite side of the movable shaft guide 410; and a stopper protrusion 440 for guiding a pivoting stop point of the chin protection bar 700.

The movable shaft guide 410 may include a first hole 411 through which a first connecting unit 510 of the following pivoting unit 500 passes and a second hole 412 in which the first connecting unit 510 can rotate and move in a straight line. It is desirable that a width of the second hole 412 is smaller than that of the first hole 411 so as to prevent the first connecting unit from being easily separated from the movable shaft guide 410 when the first connecting unit 510 passes through the first hole 411 and then moves in a straight line via the second hole 412.

Further, the pivoting guide 430 has a stepped protrusion 432 so that when a second connecting unit 520 of the following pivoting unit 500 passes through the pivoting guide 430, the second connecting unit 520 is engaged with the stepped protrusion 432 and can not be easily separated from the pivoting guide 430.

The stopper protrusion 440 is formed to protrude outward from one side surface of the fixing unit 400 and limits the maximum pivoting stop point where the pivoting unit 500 can be rotated to the maximum in upward direction of the helmet cap 100 backwardly. That is, when the pivoting unit 500 reaches the maximum pivoting stop point where the pivoting unit 500 can be rotated to the maximum in the upward direction of the helmet cap 100 backwardly, a stopper hook 530 formed in the following pivoting unit 500 is engaged with the stopper protrusion 440 formed in the fixing unit 400. Therefore, the chin protection bar 700 can not further rotate in the backward and upward directions and stops at the upper portion of the helmet cap 100 rotated backward.

The fixing unit 400 may further include a coupling unit 450 by which the fixing unit 400 is fastened to the helmet cap 100. In accordance with an embodiment of the present invention, the coupling unit 450 respectively includes first, second and third connecting members 451, 452, 453 formed in a screw thread and they are connected with the helmet cap 100 by inserting external screws. However, the coupling unit 450 is not limited to such a screw connection and it is sufficient if only the fixing unit 400 can be fastened to the helmet cap 100.

Meanwhile, the pivoting unit 500 includes a first connecting unit 510 which rotates and moves in a straight line while being inserted into the movable shaft guide 410 of the fixing unit 400; a second connecting unit 520 which moves in a straight line while being inserted into the pivoting guide 430 of the fixing unit 400; and the stopper hook 530 limiting a rotation movement of the pivoting unit 500 while being engaged with the stopper protrusion 440 of the fixing unit 400.

The first connecting unit 510 includes a circular first plate 511 and a first shaft part 512 extended from a part of a lower side of the first plate 511, and the second connecting unit 520 includes a circular second plate 521 and a second shaft part 522 extended from a part of a lower side of the second plate 521.

Further, the stopper hook 530 is formed to protrude outward from one side surface of the pivoting unit 500 and as stated above, the stopper hook 530 of the pivoting unit 500 is engaged with the stopper protrusion 440 of the fixing unit 400 at the maximum pivoting stop point of the chin protection bar 700, whereby the chin protection bar 700 can not further rotate in the backward and upward directions of the helmet cap 100.

The pivoting unit 500 may further include a coupling unit 540 and can be fixed at inner sides of left and right extending portions 710 of the chin protection bar 700 by the coupling unit 540. In accordance with an embodiment of the present invention, the coupling unit 540 includes first, second and third connecting members 541, 542, 543 formed in a screw thread and they are connected with the extending portions 710 by inserting external screws. However, in the same manner as the coupling unit 450 of the fixing unit 400, the coupling unit 540 is not limited to such a screw connection and it is sufficient if only the pivoting unit 500 can be fixed at the left and right extending portions 710 of the chin protection bar 700.

FIG. 4 is a side view of the pivoting unit 500 of the chin protection bar opening/closing apparatus 300 in accordance with an embodiment of the present invention.

As illustrated in FIG. 4, a first shaft part 512 and a second shaft part 522 are the same thickness and formed on a base member 501, and the circular first plate 511 and the second plate 521 are placed on the first shaft part 512 and the second shaft part 522 respectively. In accordance with this structure, there occurs a predetermined gap between the base member 501 and the first and second plates 511, 521. The pivoting unit 500 is inserted into the fixing unit 400 via such a gap and a procedure of connecting the pivoting unit 500 with the fixing unit 400 will be explained with reference to FIG. 5.

FIG. 5 is a detailed view of a connection between the pivoting unit 500 and a fixing unit 400 of the chin protection bar opening/closing apparatus 300 in accordance with an embodiment of the present invention.

First of all, the first connecting unit 510 of the pivoting unit 500 is inserted into the movable shaft guide 410 of the fixing unit 400. More particularly, the first plate 511 of the first connecting unit 510 passes through the first hole 411 of the movable shaft guide 410.

In this case, the first plate 511 is formed on the base member 501 at a distance equivalent to the thickness of the first shaft part 512 and the width of the first shaft part 512 is approximately the same as that of the second hole 412 of the movable shaft guide 410 so that the first connection unit 510 can move to the second hole 412 of the movable shaft guide 410 under a state that the first plate 511 passes through the first hole 411 of the movable shaft guide 410.

If the first connecting unit 510 is disposed at the second hole 412 as stated above, a peripheral portion of the second hole 412 becomes interposed between the first plate 511 and the base member 501. In this case, the first connecting unit 510 can rotate and move in a straight line via the movable shaft guide 410 but can not be easily separated from the movable shaft guide 410.

If the first connecting unit 510 moves to one end of the second hole 412 of the movable shaft guide 410, the second connecting unit 520 is positioned around the pivoting guide 430. More particularly, a front end of the second plate 521 in a direction toward the first plate 511 becomes in contact with the stepped protrusion 432 formed in the pivoting guide 430.

At this time, when a force is applied to the stepped protrusion 432 of the pivoting guide 430, the stepped protrusion 432 becomes somewhat curvedly transformed, and then the second plate 521 passes through the pivoting guide 430 when the second connecting unit 520 is pushed within the transformed space.

Meanwhile, there is a gap having a thickness equivalent to that of the second shaft part 522 between the second plate 521 and the base member 501 so that the stepped protrusion 432 of the pivoting guide 430 becomes interposed between the second plate 521 and the base member 501 when the second plate 521 passes through the pivoting guide 430. Accordingly, the second connecting unit 520 can not be easily separated from the pivoting guide 430.

Hereinafter, an operation of the chin protection bar opening/closing apparatus 300 will be explained in accordance with an embodiment of the present invention.

FIG. 6 is a partial side view illustrating a state of the chin protection bar opening/closing apparatus 300 prior to operation thereof in accordance with an embodiment of the present invention, FIG. 7 is a partial side view providing a state of the chin protection bar opening/closing apparatus under operation thereof and FIG. 8 is a partial view illustrating a state of the chin protection bar opening/closing apparatus after operation thereof.

As shown in FIG. 6, if the wearer pushes a lever (not illustrated) of the locker 200 while wearing the helmet, the helmet cap 100 and the chin protection bar 700 become unlocked and the chin protection bar 700 is able to rotate. Further, the second connecting unit 520 of the pivoting unit 500 is positioned at an end of the pivoting guide 430 and the first connecting unit 510 is positioned at the lowest point of the second hole 412 of the movable shaft guide 410.

If the chin protection bar 700 is lifted to the approximately middle position of the helmet cap 100, as illustrated in FIG. 7, the pivoting unit 500 fixed at the left and right extending portions 710 of the chin protection bar 700 is rotated together therewith so that the second connecting unit 520 becomes disposed in the middle of the pivoting guide 430. However, the second connecting unit 520 inserted into the pivoting guide 430 makes a straight-line movement centering the first connecting unit 510 instead of a rotation movement and keeps a uniform distance between the first connecting unit 510 and the second connecting unit 520 so that the first connecting unit 510 rotates and moves in a straight line in a longitudinal direction of the second hole 412 of the movable shaft guide 410 when the second connecting unit 520 moves along the pivoting guide 430.

Therefore, if the second connecting unit 520 is disposed in the middle of the pivoting guide 430, the first connecting unit 510 becomes positioned at the highest point of the second hole 412 so that the chin protection bar 700 becomes automatically spaced apart from the helmet cap 100 by a predetermined distance and becomes lifted upward.

Then, if the chin protection bar 700 is lifted higher, as illustrated in FIG. 8, the second connecting unit 520 becomes positioned at an end of the pivoting guide 430 opposite to an initial position thereof, and as stated above, the first connecting unit 510 becomes positioned at the lowest position of the second hole 412 of the movable shaft guide 410 and a state that the chin protection bar 700 is lowered toward the helmet cap 100 is maintained.

Through the above operation, the chin protection bar 700 is rotated in the backward direction of the helmet cap 100 and when the chin protection bar 700 is rotated in a forward direction of the helmet cap 100, the above operation is preceded reversely.

Further, if the chin protection bar 700 is totally rotated to a rearmost position, the stopper hook 530 of the pivoting unit 500 is engaged with the stopper protrusion 440 of the fixing unit 400 and thus the chin protection bar 700 can maintain its state that it is rotated to the rearmost position.

As stated above, in accordance with an embodiment of the present invention, since the chin protection bar opening/closing apparatus having a simple structure, instead of a complicated structure, with only a fixing unit and a pivoting unit is provided, the chin protection bar becomes rotated in the backward direction of the helmet cap while being lifted up and also it becomes rotated in the forward direction of the helmet cap while being lifted up. Therefore, it is possible to prevent a collision between the chin protection bar and the helmet cap.

Further, in accordance with an embodiment of the present invention, the simple structure of the chin protection bar opening/closing apparatus makes it possible to reduce the total weight of the helmet as well as the manufacturing cost of the helmet.

The above description of the present invention is provided for the purpose of illustration, and it would be understood by those skilled in the art that various changes and modifications may be made without changing technical conception and essential features of the present invention. Thus, it is clear that the above-described embodiments are illustrative in all aspects and do not limit the present invention.

The scope of the present invention is defined by the following claims rather than by the detailed description of the embodiment. It shall be understood that all modifications and embodiments conceived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention. 

1. An apparatus for opening/closing a chin protection bar installed in a helmet cap having a front opening, the apparatus comprising: a fixing unit which is fixed to the helmet cap and includes a movable shaft guide having an elongated hole shape and a pivoting guide formed approximately vertical to the movable shaft guide; and a pivoting unit which is fixed to the chin protection bar and includes a first connecting unit slidably inserted into the movable shaft guide and a second connecting unit slidably inserted into the pivoting guide, wherein the pivoting guide has a straight line shape, and the second connecting unit moves back and forth in a straight line in the pivoting guide and the first connecting unit moves back and forth in a straight line in the movable shaft guide according to the straight-line back-and-forth movement of the second connecting unit.
 2. The apparatus of claim 1, wherein if the second connecting unit moves from one end of the pivoting guide to the middle portion thereof, the first connecting unit is lifted from a lower side of the movable shaft guide to a upper side thereof and if the second connecting unit moves from the middle portion of the pivoting guide to the other end thereof, the first connecting unit is lowered from the upper side of the movable shaft guide to the lower side thereof.
 3. The apparatus of claim 1, wherein the first connecting unit of the pivoting unit includes a first plate and a first shaft part connected to a part of a lower side of the first plate, and the second connecting unit includes a second plate and a second shaft part connected to a part of a lower side of the second plate.
 4. The apparatus of claim 1, wherein the movable shaft guide of the fixing unit includes a first hole into which the first plate can be inserted and a second hole, which has approximately the same width as that of the first shaft and is elongated in order for the first connecting unit passing through the first hole to move in a straight line.
 5. The apparatus of claim 4, wherein the pivoting guide of the fixing unit has a stepped protrusion, whereby the second plate passing through the pivoting guide slides while being hooked on the stepped portion so as to prevent the second connecting unit from being separated from the pivoting guide.
 6. The apparatus of claim 5, wherein if the first connecting unit is disposed in one end of the second hole in a direction opposite to the first hole, the second connecting unit is elastically supported against the stepped portion.
 7. The apparatus of claim 1, wherein a stopper protrusion for limiting a rotation of the chin protection bar is formed in one side of the pivoting unit and a stopper hook corresponding to the stopper protrusion is formed in one side of the fixing unit.
 8. A safety helmet comprising: a helmet cap having a front opening; a chin protection bar which is pivotably fixed at the helmet cap for protecting a wearer's chin; and a chin protection bar opening/closing apparatus which serves as a pivoting shaft of the chin protection bar and at the same time allows the chin protection bar to rotate while being spaced apart from the helmet cap by a predetermined distance, wherein the chin protection bar opening/closing apparatus includes: a fixing unit which is fixed at the helmet cap and has a long hole-shaped movable shaft guide and a pivoting guide formed approximately vertical to the movable shaft guide; and a pivoting unit which is fixed at the chin protection bar and has a first connecting unit slidably inserted and connected to the movable shaft guide and a second connecting unit slidably inserted into the pivoting guide, wherein the pivoting guide has a straight line shape and the second connecting unit moves back and forth in a straight line in the pivoting guide and the first connecting unit moves back and forth in a straight line in the movable shaft guide according to the straight-line back-and-forth movement of the second connecting unit. 